Press tofu with a tofu press or a towel with a heavy object, like a cast iron pan on top. Press for at least 15 minutes. Cut tofu into bite sized pieces.
Cook noodles according to directions. Drain water and set aside.
Simmer the 8 cups water with kombu stalk for at least 10 minutes – longer if you want a stronger flavor. Remove stalk and chop. Put chopped kombu back in pot.
Add tofu, tamari, ginger, garlic and sliced mushrooms to pot of water. Cook for about 10 minutes. Turn off the heat.
Remove a cup or so of the water. Mix in the miso, removing the clumps. Add the miso water mixture back to the pot. This is done because you don’t want to boil the miso. It will lose its beneficial bacteria.
Spoon noodles into bowls. Top with miso soup and chopped green onions.